PURPOSE: To compare clinical outcomes of extracorporeal shockwave therapy and platelet-rich plasma injection for the treatment of lateral epicondylitis of the elbow. MATERIALS AND METHODS: Consecutive patients with a lateral epicondylitis who had refractory elbow pain more than 6 months and no response to treatment more than 3 months were recruited for this study. Diagnosis was made on the basis of physical examination and ultrasound imaging study. Prospective randomized trial was performed between two treatment groups; extracorporeal shockwave therapy versus platelet-rich plasma injection. Fifty patients for each group were allocated based on the results of power analysis. Disabilities of arm, shoulder and hand (DASH) scores obtained before treatment and at 1 year after the last treatment were compared between two groups. RESULTS: Both groups showed significant improvement of DASH scores after treatment. The patients who had platelet-rich plasma injection showed significantly greater improvement of DASH scores (from 37.0 to 11.1) than the patients who had extracorporeal shockwave therapy (from 41.9 to 29.9). CONCLUSION: Better subjective outcomes can be expected after platelet-rich plasma injection compared with extracorporeal shockwave therapy in patients with a refractory lateral epicondylitis.